Margret and H. A. took a belated honeymoon trip to Europe in 1936. Their planned two-week stay in Paris turned into four years. During that happy time, H. A. began to write and illustrate books. Zebrology, published by Chatto & Windus in London in 1937, is Rey's first title in English, although it is not a children's book. How the Flying Fish Came into Being, a similar wordless book consisting of eight illustrated panels, followed a year later. 1938 also saw the publication of Le Zoo and Le Cirque, toy books complete with animals to punch out and assemble.

When an editor at Gallimard saw Rey's whimsical drawings of a giraffe in a French periodical, he suggested that Rey write a book using it as one of the characters. Thus was born Rafi et les 9 Singes, published in 1939. An English language version was also published that same year by Chatto & Windus with the title Raffy and the Nine Monkeys. In the subsequent American edition, Raffy's name was changed to Cecily G. (G for giraffe, of course).

French children loved the antics of one of the nine monkeys named "Fifi" and begged for more stories. Fifi was soon renamed "George" and went on to fame and fortune in his own series of books